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diff --git a/doc/manual/src/glossary.md b/doc/manual/src/glossary.md index 71ff13275..70a0eb994 100644 --- a/doc/manual/src/glossary.md +++ b/doc/manual/src/glossary.md @@ -1,48 +1,100 @@ # Glossary - - derivation\ + - [derivation]{#gloss-derivation}\ A description of a build action. The result of a derivation is a store object. Derivations are typically specified in Nix expressions - using the [`derivation` primitive](expressions/derivations.md). These are + using the [`derivation` primitive](language/derivations.md). These are translated into low-level *store derivations* (implicitly by `nix-env` and `nix-build`, or explicitly by `nix-instantiate`). - - store\ + - [content-addressed derivation]{#gloss-content-addressed-derivation}\ + A derivation which has the + [`__contentAddressed`](language/advanced-attributes.md#adv-attr-__contentAddressed) + attribute set to `true`. + + - [fixed-output derivation]{#gloss-fixed-output-derivation}\ + A derivation which includes the + [`outputHash`](language/advanced-attributes.md#adv-attr-outputHash) attribute. + + - [store]{#gloss-store}\ The location in the file system where store objects live. Typically `/nix/store`. - - store path\ + From the perspective of the location where Nix is + invoked, the Nix store can be referred to + as a "_local_" or a "_remote_" one: + + + A *local store* exists on the filesystem of + the machine where Nix is invoked. You can use other + local stores by passing the `--store` flag to the + `nix` command. Local stores can be used for building derivations. + + + A *remote store* exists anywhere other than the + local filesystem. One example is the `/nix/store` + directory on another machine, accessed via `ssh` or + served by the `nix-serve` Perl script. + + - [chroot store]{#gloss-chroot-store}\ + A local store whose canonical path is anything other than `/nix/store`. + + - [binary cache]{#gloss-binary-cache}\ + A *binary cache* is a Nix store which uses a different format: its + metadata and signatures are kept in `.narinfo` files rather than in a + Nix database. This different format simplifies serving store objects + over the network, but cannot host builds. Examples of binary caches + include S3 buckets and the [NixOS binary + cache](https://cache.nixos.org). + + - [store path]{#gloss-store-path}\ The location in the file system of a store object, i.e., an immediate child of the Nix store directory. - - store object\ + - [store object]{#gloss-store-object}\ A file that is an immediate child of the Nix store directory. These can be regular files, but also entire directory trees. Store objects can be sources (objects copied from outside of the store), derivation outputs (objects produced by running a build action), or derivations (files describing a build action). - - substitute\ + - [input-addressed store object]{#gloss-input-addressed-store-object}\ + A store object produced by building a + non-[content-addressed](#gloss-content-addressed-derivation), + non-[fixed-output](#gloss-fixed-output-derivation) + derivation. + + - [output-addressed store object]{#gloss-output-addressed-store-object}\ + A store object whose store path hashes its content. This + includes derivations, the outputs of + [content-addressed derivations](#gloss-content-addressed-derivation), + and the outputs of + [fixed-output derivations](#gloss-fixed-output-derivation). + + - [substitute]{#gloss-substitute}\ A substitute is a command invocation stored in the Nix database that describes how to build a store object, bypassing the normal build mechanism (i.e., derivations). Typically, the substitute builds the store object by downloading a pre-built version of the store object from some server. - - purity\ + - [substituter]{#gloss-substituter}\ + A *substituter* is an additional store from which Nix will + copy store objects it doesn't have. For details, see the + [`substituters` option](command-ref/conf-file.html#conf-substituters). + + - [purity]{#gloss-purity}\ The assumption that equal Nix derivations when run always produce the same output. This cannot be guaranteed in general (e.g., a builder can rely on external inputs such as the network or the system time) but the Nix model assumes it. - - Nix expression\ + - [Nix expression]{#gloss-nix-expression}\ A high-level description of software packages and compositions thereof. Deploying software using Nix entails writing Nix expressions for your packages. Nix expressions are translated to derivations that are stored in the Nix store. These derivations can then be built. - - reference\ + - [reference]{#gloss-reference}\ A store path `P` is said to have a reference to a store path `Q` if the store object at `P` contains the path `Q` somewhere. The *references* of a store path are the set of store paths to which it @@ -52,11 +104,11 @@ output paths), whereas an output path only references other output paths. - - reachable\ + - [reachable]{#gloss-reachable}\ A store path `Q` is reachable from another store path `P` if `Q` is in the *closure* of the *references* relation. - - closure\ + - [closure]{#gloss-closure}\ The closure of a store path is the set of store paths that are directly or indirectly “reachable” from that store path; that is, it’s the closure of the path under the *references* relation. For @@ -71,34 +123,34 @@ to path `Q`, then `Q` is in the closure of `P`. Further, if `Q` references `R` then `R` is also in the closure of `P`. - - output path\ + - [output path]{#gloss-output-path}\ A store path produced by a derivation. - - deriver\ + - [deriver]{#gloss-deriver}\ The deriver of an *output path* is the store derivation that built it. - - validity\ + - [validity]{#gloss-validity}\ A store path is considered *valid* if it exists in the file system, is listed in the Nix database as being valid, and if all paths in its closure are also valid. - - user environment\ + - [user environment]{#gloss-user-env}\ An automatically generated store object that consists of a set of symlinks to “active” applications, i.e., other store paths. These are generated automatically by [`nix-env`](command-ref/nix-env.md). See *profiles*. - - profile\ + - [profile]{#gloss-profile}\ A symlink to the current *user environment* of a user, e.g., `/nix/var/nix/profiles/default`. - - NAR\ + - [NAR]{#gloss-nar}\ A *N*ix *AR*chive. This is a serialisation of a path in the Nix store. It can contain regular files, directories and symbolic links. NARs are generated and unpacked using `nix-store --dump` and `nix-store --restore`. - - `∅` \ + - [`∅`]{#gloss-emtpy-set}\ The empty set symbol. In the context of profile history, this denotes a package is not present in a particular version of the profile. - - `ε` \ + - [`ε`]{#gloss-epsilon}\ The epsilon symbol. In the context of a package, this means the version is empty. More precisely, the derivation does not have a version attribute. |